Say you were in charge of getting rid of a large quantity of paper - up to 1,000 in a row. It can't be used as scratch paper because it contains confidential information. It also can't be outsourced to third parties because the company isn't interested in refunding your expenses.

The scenario is real and is wasting the time of a person whose work is useful to me. The current method is tearing them all apart by hand or using a crushing machine when it's available. As mentioned, it takes a lot of time and could probably be done a thousand more efficient ways.

What is the cheapest and fastest method to destroy a large quantity of paper containing confidential information?

Who stands to lose if the destruction is not done? If it is the company that is refusing to reimburse the costs of destruction, the simple answer is to deliver the documents to their head of compliance with a suitably snarky cover letter.
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ruiefMay 16 '13 at 9:45

1

Ruief is right, if they are expecting you to dispose of materials in a security-safe manner, they should pay the expense or take care of it themselves.
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Jeff ClaytonAug 25 '14 at 20:58

7 Answers
7

The worst thing you can do is tearing them apart. It's time consuming and attacker just needs extra time and patience to put pieces together.

The same rule applies for shredding - if after shredding are left too large pieces, again, attacker just needs time and patience.

There are several shredding techniques (from wikipedia)

Strip-cut shredders, the least secure, use rotating knives to cut narrow strips as long as the original sheet of paper. Such strips can be reassembled by a determined and patient investigator or adversary, as the product (the destroyed information) of this type of shredder is the least randomized. It also creates the highest volume of waste inasmuch as the chad has the largest surface area and is not compressed.

Cardboard shredders are designed specifically to shred corrugated material into either strips or a mesh pallet.

Disintegrators and granulators repeatedly cut the paper at random until the particles are small enough to pass through a mesh.

Hammermills pound the paper through a screen.

Pierce and Tear Rotating blades pierce the paper and then tear it apart.

Grinders A rotating shaft with cutting blades grinds the paper until it is small enough to fall through a screen.

Also, there are several standards for shredding (from wikipedia)

Level 1 = 12 mm strips OR 11 x 40mm particles

Level 2 = 6 mm strips OR 8 x 40mm particles

Level 3 = 2 mm strips OR 4 x 30mm particles (Confidential)

Level 4 = 2 x 15 mm particles (Commercially Sensitive)

Level 5 = 0.8 x 12 mm particles (Top Secret or Classified)

Level 6 = 0.8 x 4 mm particles (Top Secret or Classified)

What I'm trying to say is - it's not about - "Let's torn this paper and we'll be fine!" It's about how hard is to put this pieces together. If it's next to impossible, then shredding is done well.
However, if attacker is aiming for the lowest hanging fruit, then any kind of shredding is better then none.

Example of well done shredding (once it was a money)

I guess setting them on fire or destroying them in chemical reaction would be the fastest, but this techniques should only be preformed in controlled environments by professionals!!!
Alternative is to decompose paper in water, however, it's pretty long process (10-14 days) and you'll need enough space and water to do so.

do you have a link to decomposing paper in water?
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rox0rMar 15 '12 at 3:40

@rox0r I'm sorry for late replay, but after few weeks of searching I couldn't find any link describing decomposing paper in warer. I did it about 15 years ago as school project, so only thing I can do is to edit my answer to describe how to decompose few sheets of paper. However, for larger scale, I'm in dark, unfortunately.
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StupidOneApr 17 '12 at 17:22

@rox0r It's a step in recycling paper. (You may want to look for how to make homemade paper, lots of videos on this topic are available on YouTube, and it's commonly done as a school project). Basically, paper is wooden fibers glued together (+ additives to make it white or glossy) and water separates them, breaking down the mesh. You may accelerate the process by shredding the paper sheets before putting them in water, for example with a mixer.
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ignisSep 29 '14 at 6:39

How many piece of papers do you want to destroy? 1000, 10.000, 1.000.000 ? Apart by hand and using crashing machine sound good.But also, you can burn them. Cheap and fast. And it doesn't take much time.

There are document shredding services. You place your to be shredded confidential docs in a bin, it gets picked up and shredded/incinerated. Since your company doesn't sound interested in saving money by outsourcing it, you are left with shredding them. (Tearing apart by hand is slower than shredding.)

One of the biggest issues with burning is that you end up with either unburned product (i.e. white paper with writing) or burned product (blackened paper with obscured writing). Data can be recovered from both pretty easily. Everything has to be reduced to ash, no exceptions. Take pictures, and cook hot dogs.

Of course, you may not be allowed to burn stuff depending on your work safety practices. You're stuck with crosscut shredding, disbursing the shreds, and distributing the piles into multiple bins. A royal pain, but if you can't burn them it's your only other option.

A good long soak in a large tub of water will do the trick too. Stir daily, and leave the paper in there until it turns into goo.

No matter what, secure some approval for this method. The last thing you want is for somebody to come back and say the job wasn't done right. Also, if they reject all your options, you have a reason to tell them to dispose of their own data how they like.

+1: burning is the only real secure method, provided you really burn everything. There are so many research being done about reconstructing shreded papers that I wouldn't trust it.
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woliveirajrSep 13 '11 at 18:11

Just chiming it to point that "unshredding" is not purely theoretical. It was done on a large scale with East German archives when the Iron Curtain fell, in order to determine (among other things) who was snitching on who.

I just came across this thread by accident. By chance I've had exactly this problem recently. Instead of buying an expensive high quality shredder like the above suggests I tried disposing of everything in a big bucket of water.

To speed up the process, i used a blender to make it into a soup-like consistency/paste. I also added some bleach for good measure...

Just make sure you put more water in than you do paper otherwise it gets difficult. For about 12,000 pages of text we used about 10 buckets.

We disposed of some of it by flushing it down the toilet, and the majority of it by pouring it into bags and chucking it in the bin. Finally, we planned on turning some into dried out paper-bricks to burn for fires (for warmth!)